Flexible reduced graphene oxide supercapacitors processed using atmospheric-pressure plasma jet under various temperatures adjusted by flow rate and jet-substrate distance

Abstract

We vary the substrate temperature by adjusting the nitrogen flow rate and jet-substrate distance during nitrogen atmospheric-pressure plasma jet (APPJ) processing of screen-printed reduced graphene oxides (rGOs) on carbon cloth. The APPJ-processed rGOs on carbon cloth are then used as electrodes for supercapacitors. Increasing the nitrogen flow rate could reduce the gas temperature and enhance the reactivity of the reactive plasma species. Typically, lowering the temperature slows down the chemical reaction; however, increased reactivity of the reactive plasma species at the same jet-substrate distance could compensate the temperature effect. A nitrogen APPJ could improve the wettability of the screen-printed rGOs on carbon cloth. We found that 20-s APPJ treatment increases the areal capacitance from 6.2 mF cm-2 (without APPJ treatment) to 22.4 mF cm-2 (700 °C, 30 slm), as evaluated by galvanostatic charging/discharging (GCD) measurements under a constant current of 0.25 mA. Further, 20-s nitrogen APPJ processing at temperatures of ∼600 °C-700 °C could obtain the best areal capacitance value. The capacitance value of the fabricated flexible rGO supercapacitor remains at similar level after 1000-cycle mechanical bending test with a bending radius of 5 mm.